Try loading an image in your computer and look at Exif data. If the "Image number" is available it should show up there. If you cannot get the Exif data in your computer, load to Flickr. It should be available there.

@golf007sd, there is also a "Nikon" tab on that same dialog that calls the same value "shutter count". The reason I like reveal is that it's a tiny standalone program that displays all of the EXIF data. I grew up on unix so I guess I have a tool mentality. Most apps are like Swiss army knives with a small chainsaw attached. Yes, you can use that Phillips head screwdriver on the knife in a pinch, but I like a real (standalone) screwdriver for most tasks. Really just boils down to personal preference I guess :-}

You have a lovely camera that is almost brand new! I sold mine to get a D800 and whilst I love the D800, I miss the D700 that was by far the best (digital) camera I ever owned. I wish I could have kept it but.........